1. Field of the Invention
This invention relates to a distributed automation system comprising a programmable logic controller connected to programmable logic controllers and equipped with a host unit and couplers communicating with the said host unit through the back panel bus, one of the couplers being connected to associated equipment through a bus.
2. Discussion of the Background
Conventionally, an automation system is segmented at several levels. At the lower level, there is the sensors/actuators bus that enables exchanges between programmable logic controllers or digital controls and sensors and actuators associated with them. At the upper level, there is a computer type bus connecting the computers carrying out supervision and the production site information system. At an intermediate level, there are the buses that form the junction between the previous levels. Therefore, this assembly is heterogeneous.
The use of the TCP/IP protocol and software adapted to this protocol to enable communication at different levels between equipment on an automation network, for example using an Ethernet type bus, is well known. Programmable logic controllers are then equipped with a TCP/IP module or coupler. This solution can federate several levels.
The Java language is considered for automation components at different levels, for example for supervision management and for production management. For example, refer to articles published in the May-June d1997 issue of CiMax, or in the May 1998 issue of Measures. The Java language has advantages related to portability and object orientation, and the possibility of executing programs written in Java called xe2x80x9cappletsxe2x80x9d and imported through the network using a browser on a local station.
The purpose of this invention is to provide a hardware and software platform that makes a programmable logic controller active on an Intranet type network or its extensions by manipulation and/or production of manufacturer information, in other words xe2x80x9cnot involvedxe2x80x9d directly in real time instrumentation control and defining an object model adapted to the current structure of PLCs. It can be used to integrate industrial programmable logic controllers into a company information system without modifying the structure of PLCs. This satisfies the increasing need for integration of equipment forming part of the production facility and management systems (Supervisors, Automated production system, etc.).
The system according to the invention is characterized essentially by the fact that the coupler can communicate with associated equipment using the TCP/IP protocol using a server function, and it is provided with a mass memory containing firstly xe2x80x9cPLC variablexe2x80x9d type software objects that manage access to PLC variables, and secondly to xe2x80x9cmanufacturerxe2x80x9d type software objects that transform information from PLC variable objects to manufacturer type information that be used by the associated equipment.